Means for producing intense periodic x-ray beams of short duration



Nov. 1, 1927. 1,647,478

F. 5. SMITH MEANS FOR PRODUCING INTENSE PERIODIC X-RAY BEAMS OF SHORT DURATION Filed Feb. 15, 1924 A, I I

ATTORNEY Patented Nov. 1, 1927.

UNITED STATES 1,647,478 PATENT OFFICE.

FRANKLIN S. SMITH, OF BROOKLYN, NEW YORK, ASSIGNOR TO THE PRODUCTS PRO- TECTION CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

MEANS EOR PRODUCING INTENSE PERIODIC X-RAY BEAMS 013 SHORT DURATION.

Application filed February 15, 1924. Serial No. 693,149.

This invention relates to X-ray apparatus and systems.

. One of the objects of this invention is to provide a thoroughly practical X-ray apparatus and system' capable of periodically producing intense X-ray beams of relatively short duration. Another object is to provide I an apparatus and system of the above-mentioned nature in which great intensity of X-ray beam emanations may be achieved in a thoroughly safe and dependable manner. Another object is to provide an arrangement for dependably' exciting an X-raytube by impulse voltages. ,Another object is"to provide an apparatus of the above-mentioned character capable of continuous operation for periodically exciting one or more X-ray tubes to eflect periodic emanations of X-ray beams of the desired character. Another obj ect'is to provide a thoroughly'eflicient yet simple arrangement for heatin the cathode filament of an X-ra tube or tu es to a temperature suificient or the emission of elec-- trons and moreover to achieve such heating of the cathode filament periodically to effect X-ray emanations of the desired character. Other objects will be in part obvious or in part'pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of partsas will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims.

In order that the invention may be more readily understood and its novelty and practical advantages more fully appreciated reference may be vhad to the accompanying 4 drawing in which I have indicated more .or

less schematically one form of construction constituting an embodiment of the invention.

- Before proceeding with a description in detail of the invention and the apparatus in 4 which it is embodied and by which it maybe practiscd, reference will be made to one of the uses to and for which it may beadapted. A number of years ago I discovered (see United States Letters Patent'No. 924,284,

dated June 8, 1909) that insect life could be destroyed by the action of X-rays thereon and that by the treatment of articles or products such as cereals, tobacco, furs, etc. such insects as might be present therein could be destroyed. Subsequently I discovered that the energy of excitation of a given X- ray tube necessary for a lethal dose decreased with voltage increase and with decrease of time of application. Therefore it Wlll be apparent from the characteristics of the invention as indicated in the statement of the objects and advantages of the same that by its use a highly advantageous apparatus and system are afiorded for the de-. struction of insect life.

Referring now to the drawing, A and B designate t e low alternating voltage supply mains connected with which there are six circuits designated 1, 2, 3, 4, 5 and 6, respectively.

The circuit 1 comprises a step-up transformer 9, one end of the secondary of which is grounded 'at 9 while the other end is connected'to the cathode end of a. kenotron '10 and also to the anode end of a kenotron 11. The first of these kenotrons, 10, is connected to a high resistor 12 which is connected with the junction 13. From. this point connection 1s made to one side of a" high voltage permittor 14. The other side of the latter is grounded at 15. The kenotron 11' is connected through a high resistor 16 tothe junction point 17 From this point connection is made to one side of a high voltage permittor 18 the other side of which also is grounded at 15. From the junction point 13 connection is made at 19 with the cathode ends of two X-ray tubes 20 and 21 of the hot cathode type. From the junction 17 connection is made at 22 with the anticathode ends of the said tubes. The said anticathodes are of the water-cooled t' pe.

The tubes 20 and 21 are arranged in multiple in the discharge circuit of the permlttors 14 and 18.

The circuit 2 comprises a step-down transformer 23 the secondary of which is insulated from the primary for half the voltage of the X-ray tube excitation. The said transformer 23 excites the filament or cathode 24 of kenotron 10 through the variable reactance 25.

The circuit 3 is similar to circuit 2. It comprises a step-down transformer 26, variable reactance 27 and filament 28 and it operates to excite the latter.

The circuit 4 comprises an induction motor 29 which drives through a shaft 30 of insulating material the pump 31. T1115 motor 119 also drives by means of a belt 32 the fan 33. The purpose of the apparatus described in connection with and as operated by this circuit is to effect circulation of water through the inlet pipes 34 and 35 and outlet pipes 36 and 37 and the radiator 38, for cooling the anticathodes' 38" and 38 of the X-ray tubes 20 and 21. The shaft 30 of insulating material insulates the motor 29 from the pump 31 for half the voltage of the X-ray tube excitation.

The circuit 5 comprises a synchronous motor 39 which by means of a shaft 41 of insulating material drives a direct current generator 42. The insulating shaft 41 affords insulation for half the voltage of the X-ray tube excitation. The generator 42 is connected through low resistor 43 to one side of a low voltage permittor 44 through the junction 45. From the junction 45 multiple connection is made through variable resistors 46 and 47 with the filaments 48 and 49 of the X-ray tubes 20 and 21. The filaments are connected in multiple with the sphere 50 which with a sphere 51 forms a fixed spark-gap. The spheres 50 and 51 are insulated from each other for the full voltage of the generator 42. The sphere 51 is connected to junction 52 from which connection is made to the other side of the permitter 44 and to a circular ring sector 52 COHStitlltlIlg one side of a switch designated as a whole at 53. The other side consisting of a ring sector 53 of the switch 53 is connected to the generator 42 by means of connection 53 The generator 42 drives a cir- Quit controlling contactor 54 through reducing gears 55. The contactor 54 is .carried by an arm 56 of insulating material. The end of the insulating arm 56 is provided with a metallic sph'erc 57 which functions in circuit 6 as will be hereinafter described.

The said circuit 6 comprises a step-up transformer 58 of intermediate voltage, one side orone end of the secondary of which connected through kenotron 10 and resistor 12 to junction 13. From junction 13 connection is made to one side of a permittor 59 of intermediate voltage andto the sphere 50 to which reference has been made previously. The other side of the secondary of the transformer 58 is connected to the other side of the permittor 59 and to a metallic sphere 60 which with sphere 61 forms a fixed spark-gap. Sphere 61 is connected to the sphere 51 previously referred to, thus placing the spark-gaps between the spheres 50 and 51 and 60 and 61 in series.

At this point, it might be noted that one of the principles upon which a' hot cathode X-ray tube depends for its operation is the fact that a highly evacuated space containing two metallic electrodes, one of which is incandescent and the other cold, possesses mamas that R shall be a unilateral conductivity. In such a tube current will pass therethrough only when the negative electrode is incandescent. The intensity of the X-radiation is precisely controlled by the temperature of the cathode filament. A sensitive control of the temperature of the cathode filament is important because a small change in the filament heating current causes a great change in the tube excitation current; for example, a ten percent. (10%) change in the heating current causes a three hundred percent. (300%) change in the tube excitation current. The life of atube is somewhat dependent upon the rate of evaporation of the filament and obviously the rate of evaporation is dependent upon temperature.

Each of the high voltage permittor-s 14 and 18 is slowly charged by the rectified voltage of the transformer 9 through the kenotrons 10 and 11 and the resistors 12 and 16 to the maximum transformer voltage. Therefore the voltage across the said permittors 14 and 18, which is the exciting voltage of the X-raytubes 20 and 21, is double the maximum transformer voltage. The connections to the tubes 20 and 21 are made at the points 19 and 22, as heretofore stated, so that the inductance of the tube circuits will be equal. During the time that the permittors 14 and 18 are being charged the cathodes 48 and 49 of the X-ray tubes 20 and 21 are cold or rather their temperature isbelow that at which electron emission-is appreciable. During such periods the said tubes are therefore non-conducting. It is this feature which makes it possible to achieve such advantages as flow from the connection of the permittors directly to the X-ray tubes without a series sparlcgap in,

the exciting voltage circuit.

The intermediate voltage permittor 59 is slowly charged by half-wave rectification through kenotron 10 and resistor 12 by the intermediate voltage transformer 58. It is desirable that the relative polarities of the transformers 58 and 9 shall be such that kenotron 10 passes current alternately from said transformers. The discharge circuit of the permittor 59 is as shown on the drawing across the two fixed series spark-gaps formed by thespheres 50 and 51 and 61 and 60. The inductance of this circuit should be as low as practical and the constants such greater than 4L divided 4L 2 l The discharge'then will be logarithmic or non-oscillatory. i

by C.

During the time that the contactor 54 is in contact with the members 52* and 53f of the switch, thus to interconnect the latter and thus to connect the generator 42 to the permittor 44, the latter 1s charged through the low resistance 43. The generator 42, preferably a direct current generator, is driven preferably by the synchronous motor 39, the constant speed characteristics of the latter'thus assuring reasonably close constancy of voltage of the generator 42 for charging the permittor 44. Thus, an important advantage is achieved in that the permittor 44 is, in the course of its successive periods of charge, brought to substantially the same charge each time as the cyclic operation of the apparatus continues and thus there is assured a closely constant source of energy for bringing the cathodes 48 and 49 to incandescence.

The purpose of the permittor 44 is to store the energy with which, upon its discharge, to heat the cathodes 48 and 49 to incandescence. It is desirable that the temperature of the cathodes shall be raised at the highest practical rate. The inductance of the discharge circuit preferably is as low as practical and the constants preferably the same as outlined for the discharge circuit of the permittor 59. Thus a high rate of discharge of the permittor 44 through the cathode or cathodes of the X-ray tube or tubes may be achieved and the temperature of the cathodes raised at a correspondingly high rate.

The variable resistors 46 and 47, which preferably are of negative temperature coeflicient, are for the purpose 'of balancing the electron emission of the cathodes 48 and 49 which are of pofitive temperature coefficient. From time to time such balancing will be found to be necessary because of slight differences in manufacture and of changes in resistivity caused by evaporation.

.'During the time that the contactor 54 is in contact with the members 52 and 53, of the switch 53 all of the permittors previously referred to are being charged and by the time that the contactor 54 pa-ses out of and 51, 61 and 57, and 57 and 60. This dis-' contact with the parts 52 and 53* into the space between the adjacent opposing ends thereof to open the switch, the permittors have become "fully charged. At the moment of opening of the switch, the sphere 57 upon the outer end of the arm 56 of insulating material moves into osition between the spheres 60 and 61 so t at the permittor 59 discharges throu h its discharge circuit comprising the spar -gaps between spheres 50 charge of the permittor 59 causes the ionization of the air between the sphere electrodes 50 and 51,thus making conductive the space therebetween and thus closing the dis charge circuit of the permittor 44 through the cathodes 48 and 49; the permittor 44 in thus rapidly discharging through the X-ray tube cathode or cathodes, effects, through the resultant discharge current, the heating to incandescence of the cathode or cathodes at a very rapid rate. When the temperature of the cathodes is suflicient for appreciable electron emistion and it will be seen that the heating of the cathodes to incandescence takes place very quickly, then the permittors 14 and 18 discharge through and excite the X-ray tubes 20 and 21. The exciting voltage discharge should be made dead beat, or logarithmic. The temperature of the cathodes falls to non-appreciable electron emission temperature and the cycle restarts. A package of inteet infested material, such as cereal, is shown at 64 in position for treatment upon the supporting means 65, which may be a conveyer, with one span thereof traveling between the X-ray tubes 20 and 21.

It will be apparent to those skilled in the art that instead of using the kenotron method of charging the permittors any other suitable rectifying means may be substituted.

It 's also to be understood that any other suita le means than that shown may be employed for enabling the passage of current as or when desired through the discharge circuit of the permittor 44 vand alo that any other steep wave front means may be substituted for the cathode exciting permit-- tor or permittors 14 and 18.

It will be apparent that by, my invention I have provided means whereby intense periodic X-ray beams may be produced in an efiiczent manner.

As man made of tie above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown inthe accompanying drawing, is to be interpreted as illustrative and not in a limitpossible embodiments may be Q 2. In apparatus for producing intense periodic X-ray beams of short duratioirfthta combination of a high voltage permittor, a discharge circuit for said perm-'ttor compris'ng an X-ray tube therein," the cathode of said tube being normally at a temperature insuflicient for electron emission, and means efl'ectiveperiodically for heating the said cathode to a temperature sufiicient for electron emission, thereby to effect in said X-ray tube the periodic production of X- ray beams.

In apparatus for producing intense periodic X-ray beams of short duration,-the combination of a high voltage permittor, means for periodically charging the said permittor, a discharge circuit for said permittor comprising an X-ray tube the oath ode of which is norma ly at a temperature insufficient for electron emission, and means for heating the said cathode to a temperature sufiicicnt for electron emission.

4. In apparatusfor producing intense pcriodic X-ray beams of short duration, the combination of a high voltage permittor, a discharge circuit for said permittor, said circuit comprising a plurality of X-ray tubes in multiple, the cathode filaments of said tubes being normally at a temperature insufficient for electron emiss on, and means for discharging a current through said filaments to effect heating thereof to a tempera ture sufficient for electron emission whereby the said permittor may discharge through the said X-ray tubes.

5. In apparatus for producing intense periodic X-ray beams of short duration, the combination of high voltage permittors, a discharge circuit for sail permittors comprising a plurality of X-ray tubes in multiple the cathodes of Which are normally cold, a permittor having a discharge circuit Including the said c'thodes in multiple and including also a fixed spark-gap, and means whereby the said second named permittor is caused to discharge through its discharge circuit to effect heating of the said cathodes to incandescence whereby the first named permittor is caused to discharge through the said X-ray tubes.

6. In apparatus for producing intense periodic X-ray beams of short duration, the combination of a plurality of high voltage permittors, a transformer for charging said permittors, means whereby the, voltage across the said permittors is double the maximum transformer Voltage, a discharge circuit for the said permittors comprising an X-ray tube the cathode of which is normally of a temperature insufficient for electron emission, a permittor having a discharge circuit including the said cathode and also including a fixed spark-gap, and means for automatically ionizing at intervals the air within said gap to render the said discharge circuit conducting whereby the filament of said cathode is rendered incandescent to therebyenable the first named permittors to be discharged through the said tube.

7. In apparatus for producing intense periodic- X-ra'y beams of short duration, the combination of high voltage permittors, means whereby the said permittors are adapted to be charged with avoltage across the same which is double that of the charging means, a discharge circuit for the said permittors comprising a plurality of X-ray tubes in multiple, the cathode filaments of which are normally of a temperature insufficient for electron emission, a permittor having a discharge circuit including the said cathode filaments in multiple and also including a fixed spark-gap, a third permittor having a discharge circuit including. the said fixed spark-gap, means whereby the SllCl last mentioned permittor is adapted to be discharged through its circuit to effect ionization of the air within the said fixed spark-gap to permit discharge of the-second named permittor to effect heating of the said cathode filaments to incandescence to thereby permit discharge of the first named permittors through the said X-ray tubes.

8. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a source of electrical energy, said filament cathode, and two spaced electrodes; and means for ionizing the gas between said electrodes and for thus making conductive the space between said two spaced electrodes, thereby to make effective said energizing circuit. I

9. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a source of electrical energy, said filament cathode, and two spaced electrodes; and means for periodically making conductive the space between said two spaced electrodes, thereby to make said energizing circuit periodically effective for the production of periodic emanations of rays from said tube.

10. In X-ray apparatus, in combination, an X-ray tube; an energizing circuit associated therewith and having included therein an electrode ofsaid tube, a source of potential and a spark gap; a permittor; a source of charging potential for said permittor; and a discharge circuit for said permittor having included therein said spark gap and a cirdependent of said source of potential for ionizing said gap, thereby to render said energizing circuit conducting.

12. In X-ray apparatus, in combination,

an X-ray tube; an energizing circuit associated therewith and having included therein an electrode of saidtube, a source of potential and a spark gap; apermittor; and a source of charging potential for said permittor, said permittor being connected across said spark gap and being adapted upon discharge across said gap to ionize the gas therein, thereby to render said energizing circuit conducting. 13. In X-ray apparatus, in combination, an-X-ray tube; an energizing circuit associated' therewith and having included therein an electrode of said tube, a source of potential and a spark gap; and a source of potential for breaking down said spark gap, thereby to render said energizing circuit conductin %4. In X-ray apparatus, in combination, an Xray tube; and energizing circuit associated therewith and having included therein I an electrode of said tube, a source of potential and a spark gap; a permittor; a source of charging potential for said permittor; a discharge circuit for said permittor having includedtherein said spark gap and a second spark gap; and means for caus ng said permittor-to discharge across both said spark gaps, thereby to render said first-mentioned spark gap conductive and to render said energizing circuit efiective.

15. In X-ray apparatus, in combination, an X-ray tube having afilament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for sa d filament cathode having included therein a permittor and said filament cathode; means for causing said permittor to dischar e through said filament, thereby to heat the atter; and

means for charging said permittor.

16. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor, said filament cathode, and a spark gap; means for charging said permittor; and means for breaking down said spark gap 'to cause said permittor to discharge through said filament cathode.

1'1. In X-ray apparatus, in comb nation an X-ray tube having a filament cathode an ananode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor, said filament cathode, and two spaced electrodes; means for charging said ermit tor; and means for making conductive the space between said two spaced electrodes, thet l'eby to make efiective said energizing circui 18. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said fila ment cathode having included therein a permittor, said filament cathode and a circuit contrplling device; means for charging said permittor; and means for periodically operating said circuit controlling device to effect periodic discharges of said permittor through said energizing circuit.

19. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor and said filament cathode;means for charging said permittor; and means for conan anode; means forming a source of high potential connected across said cathode and 4 anode; an energizing circuit for said filament cathode having included therein a permittor and said filament cathode; means for charging said permittor; and a mechanically actuated switch fonefiecting periodic discharge of said permittor through said energizing circuit. thereby to heat said filamenta 22. In X-ray apparatus in combination, an X-ray tube; an energizing circuit associated therewith and having included therein an electrode of said tube, a source of po tential and a spark gap; and means for causing said spark gap to become conductive, said means including a permittor and a second spark gap, said. permittor being connected across said two spark gaps in series,-and means for reducing said second-mentioned spark gap, thereby to cause said permittor to discharge across both of said spark gaps; and means for charging said permittor.

23. In X-ray apparatus, in combination, an X-ray tube; an energizing circuit associated therewith and having included there in an electrode of said tube, a source of potential and a spark gap and means for causing said spark gap to become conductive,

said means including a permittor and a second spark gap, said permittor bBlIlgCOIlIlGCted across said two spark gaps in series, and a mechanically actuated device for periodical- 1y reducing said second-mentioned spark gap, thereby to effect periodic discharge of said permittor across both of said spark gaps, and means for charging said permittor.

24. In X-ray apparatus, in comb nation, an X-ray tube; an energizing circuit associated therewith and having included therein an electrode of said tube, a source of potential and a spark gap; and means for causing said spark gap to become conductive, said means including a permittor and a sec-' ond spark gap, said permittor being connected across said two spark gaps in series, a mechanically actuated electrode periodically movable between the electrodes of said second-mentioned spark gap for effecting a periodic discharge of said permittor across both of said spark gaps; and means for charging said permittor.

25. In X-ray apparatus,jn combination, an X-ray tube; an energizing circuit associated therewith and having included therein an electrode of said tube and a permittor; a charging circuit for said permittor having included therein a sourceof potential for charging said permittor; and a switch adapted one position to make effective said charging circuit and said energizing circuit ineffective and in another position to make ineffective said charging circuit and to make effective said energizing circuit.

26. In X-ray apparatus, in combination, an X-ray tube; an energizing circuit associated therewith and having included therein an electrode of said tube and a permittor; a charging circuit for said permittor having included therein a source of potential for charging said permittor; a switch adapted in one position to make effective said charging circuit and said energizing circuit ineffective and in another position to make ineffective said charging circuit and to make effective said energizing circuit; and means for sequentially moving said switch from one position to another.

27. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor and said filament cathode; a charging circuit for said permittor having included therein a source of potential for charging the latter; and a switch adapted in one position to make efiective said charging circuit and said energizing circuit ineffective and in another position to make ineffective said charging circuit and to make effective said energizing circuit.

28. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode havin included therein a permittor and said filament cathode; a charging circuit for said permittor having included therein. a source of potential for charging the latter; a switch idapted in one position to make effective said charging circuit and said energizing circuit-ineffective and in another position to make inefi'ective said charging circuit and to make eflective said energizin circuit; and means for sequentially moving said switch from one position to another.

29. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor, said filament cathode, and two spaced electrodes; a charging circuit for said permittor; a switch adapted in one position to make effective said chargin circuit and in another position to open said charging circuit; and means controlled by said switch when in its second-mentioned position for making conductive the space between said two electrodes.

30. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a permittor, said filament cathode, and a spark gap; a charging circuit for said permittor; a source of potential for breaking down said spark gap; and a switch adapted in one position to make effective said charging circuit and in another position to make efi'ective said last-mentioned source of potential to break down said spark gap.

31. In X-ray apparatus, in combination, an X-ray tube having a filament cathode and an anode; means forming a source of high potential connected across said cathode and anode; an energizing circuit for said filament cathode having included therein a' permittor, "said filament cathode, and a spark gap: a charging circuit for said permittor; a source of potential for breaking down said spark gap; a switch adapted in one position to make effective said charging circuit and in another position to make efiective said last-mentioned source of potential to break down said spark gap; and means forsequentially moving said switch from one position to another.

32. In X-ray apparatus, in combination,

ated therewith and havlng included therein an electrode of said tube, a permittor, and a spark ap; a charging circuit for said permittor aving included therein a source of potential for charging the latter; a source of potential for breaking down said spark and a switch operating first to make effective said charging circuit, thereby to charge said permittor, and then .to make efiective said last-mentioned source of po-', tential for breaking down said spark gap, 1 0 V to make eifective said energizing v j] thereby circuit. In testimony, that I claim the foregoing as my invention I have hereunto signed my name this 13th day of February, 1924. FRANKLIN S. SMITH. 

